Fused circuits and relays. (or not)

 

Fused/Unfused  Circuits

54-1871 has a fuse block containing a grand total of two fuses, with most of the stock wiring still in place,   even the melted sections.   The fuse block has essentially two sections - ignition (energized by the ignition key) and auxiliary (energized irrespective of the ignition key).  For each of those there is a fuse.    One side of the fuse is energized, this is the feed side.  The other, "downstream"  side of the fuse is the fused side.  Circuits may be connected to either the feed side (unprotected by the fuse) or the fused (protected) side.   The table below identifies the connections to the fuse block using that logic. 

There are also a significant number of circuits, in fact the higher current ones, that are unfused.   One reason for this is that the ammeter is not a shunt type, and requires that the current pass through it in order to be measured.   The ammeter therefore precedes the fuse block in the car's wiring, and several circuits, branch from here, the fuse block incorporating two of these.   The table below identifies the unfused circuits.

The photo below shows 54/1871's fuse block below a later  (damaged) Twincam fuse block.

Relays

Interestingly the S2 wiring diagram identifies only two relays (rad fan and main relay plus the two flashers.  (turn and hazard).

The service manual depicts five relays, main, fan, side, (what is that?) dip, and horn. 54/1871 had some relays in addition to the basic two, but I have no idea whether they were original.

Here, from the parts manual.Omitting the main charging relay, Only 13, 14 and 21 were indicated for the type 54.   Hazard, Turn, fan motor.

It can be concluded that 54/1871 had only the rad fan relay in the front runck, and that the horn, lights, and vent fan were controlled directly via the fascia switches.

Updating 54/1871

I would seem worthwhile to update the fuse block and to incorporate relays for higher current loads, given the age and light gauge of the wire employed throughout.  Fortunately, newer fans and led lighting will reduce the total current required.   If the Ammeter were dispensed with, the carge curcuit coud be directly wired and  much of the wiring could be more easily protected by an additional fuse  or two.

Fuses

Easy fixes:   If the brown wire feeding the ammeter was fused at source this would address some risk as would fusing the window circuit at the fuse block.   (the wiring is located correctly however the stock fuse block lacked capacity.   So they didn't protect the circuit....  

The circuits which connect to the ammeter (in the unfused table above) will require some rewiring or bypassing of the ammeter to simplify and protect.  These could be broght to a new fuse panel.

If the front trunk is to be provided a heavier gauge feed for both the auxiliary and ignition circuits, it may make sense to add additional fusing in the front trunk, likely part of a combined relay/fuse enclosure.  The existing wiring and fusing would supply the relays' control circuit only and possibly the washer pump directly.  This would significantly lower the loads passing through the unfused light switch, steering column stalks and related wiring.  This could be seperately protected with an in-line fuse if required.    

Relays

A start relay should be added.   This will power the solenoid, ECU, possibly the fuel pump, charging system - if these are not already incorporated into the ECU.

It would be easy to conclude that the front trunk will require relays for high and low beams, rad, horn, fresh air blower, however the loads imposed by modern lights and motors may make this unnecessary..

Accessories

Consideration should be given to a USB charger, possibly in the glove niche or simply on the console.

Modern radio/stereos need to be investigated.   It is possible that a remote unit should be located... remotely, possibly in the front.  It is very unlikely that music will be audible however a unit with a BT connection for phone or gps operation etc might be a good idea.  

Depending on the ECU and EFI setup chosen, it may make more sense to incorporate connections and a perch for a small tablet/display.